Understanding Command Modes

The Cisco IOS user interface is divided into many different modes. The commands available to you depend on which mode you are currently in. Enter a question mark (?) at the system prompt to obtain a list of commands available for each command mode.

When you start a session on the switch, you begin in user mode, often called user EXEC mode. Only a limited subset of the commands are available in user EXEC mode. For example, most of the user EXEC commands are one-time commands, such as show commands, which show the current configuration status, and clear commands, which clear counters or interfaces. The user EXEC commands are not saved when the switch reboots.

To have access to all commands, you must enter privileged EXEC mode. Normally, you must enter a password to enter privileged EXEC mode. From this mode, you can enter any privileged EXEC command or enter global configuration mode.

Using the configuration modes (global, interface, and line), you can make changes to the running configuration. If you save the configuration, these commands are stored and used when the switch reboots. To access the various configuration modes, you must start at global configuration mode. From global configuration mode, you can enter interface configuration mode and line configuration mode.

Table 2-1 describes the main command modes, how to access each one, the prompt you see in that mode, and how to exit the mode. The examples in the table use the hostname Switch.

Table 2-1 Command Mode Summary

Mode

Access Method

Prompt

Exit Method

About This Mode

User EXEC

Begin a session with your switch.

Switch>

Enter logout or quit.

Use this mode to

•Change terminal settings.

•Perform basic tests.

•Display system information.

Privileged EXEC

While in user EXEC mode, enter the enable command.

Switch#

Enter disable to exit.

Use this mode to verify commands that you have entered. Use a password to protect access to this mode.

Global configuration

While in privileged EXEC mode, enter the configure command.

Switch(config)#

To exit to privileged EXEC mode, enter exit or end, or press Ctrl-Z.

Use this mode to configure parameters that apply to the entire switch.

Config-vlan

While in global configuration mode, enter the vlanvlan-id command.

Switch(config-vlan)#

To exit to global configuration mode, enter the exit command.

To return to privileged EXEC mode, press Ctrl-Z or enter end.

Use this mode to configure VLAN parameters. When VTP mode is transparent, you can create extended-range VLANs (VLAN IDs greater than 1005) and save configurations in the switch startup configuration file.

VLAN configuration

While in privileged EXEC mode, enter the vlan database command.

Switch(vlan)#

To exit to privileged EXEC mode, enter exit.

Use this mode to configure VLAN parameters for VLANs 1 to 1005 in the VLAN database.

Interface configuration

While in global configuration mode, enter the interface command (with a specific interface).

While in global configuration mode, specify a line with the line vty or line console command.

Switch(config-line)#

To exit to global configuration mode, enter exit.

To return to privileged EXEC mode, press Ctrl-Z or enter end.

Use this mode to configure parameters for the terminal line.

For more detailed information on the command modes, see the command reference guidefor this release.

Understanding the Help System

You can enter a question mark (?) at the system prompt to display a list of commands available for each command mode. You can also obtain a list of associated keywords and arguments for any command, as shown in Table 2-2.

Table 2-2 Help Summary

Command

Purpose

help

Obtain a brief description of the help system in any command mode.

abbreviated-command-entry?

Obtain a list of commands that begin with a particular character string.

For example:

Switch# di?

dir disable disconnect

abbreviated-command-entry<Tab>

Complete a partial command name.

For example:

Switch# sh conf<tab>

Switch# show configuration

?

List all commands available for a particular command mode.

For example:

Switch> ?

command?

List the associated keywords for a command.

For example:

Switch> show ?

command keyword?

List the associated arguments for a keyword.

For example:

Switch(config)# cdp holdtime ?

<10-255> Length of time (in sec) that receiver must keep this packet

Understanding Abbreviated Commands

You need to enter only enough characters for the switch to recognize the command as unique.

This example shows how to enter the show configuration privileged EXEC command in an abbreviated form:

Switch# show conf

Understanding no and default Forms of Commands

Almost every configuration command also has a no form. In general, use the no form to disable a feature or function or reverse the action of a command. For example, the no shutdown interface configuration command reverses the shutdown of an interface. Use the command without the keyword no to re-enable a disabled feature or to enable a feature that is disabled by default.

Configuration commands can also have a default form. The default form of a command returns the command setting to its default. Most commands are disabled by default, so the default form is the same as the no form. However, some commands are enabled by default and have variables set to certain default values. In these cases, the default command enables the command and sets variables to their default values.

Understanding CLI Error Messages

Table 2-3 lists some error messages that you might encounter while using the CLI to configure your switch.

Table 2-3 Common CLI Error Messages

Error Message

Meaning

How to Get Help

% Ambiguous command:
"show con"

You did not enter enough characters for your switch to recognize the command.

Re-enter the command followed by a question mark (?) with a space between the command and the question mark.

The possible keywords that you can enter with the command appear.

% Incomplete command.

You did not enter all the keywords or values required by this command.

Re-enter the command followed by a question mark (?) with a space between the command and the question mark.

The possible keywords that you can enter with the command appear.

% Invalid input detected
at `^' marker.

You entered the command incorrectly. The caret (^) marks the point of the error.

Enter a question mark (?) to display all the commands that are available in this command mode.

The possible keywords that you can enter with the command appear.

Using Configuration Logging

Beginning with Cisco IOS Release 12.2(25)SED, you can log and view changes to the switch configuration. You can use the Configuration Change Logging and Notification feature to track changes on a per-session and per-user basis. The logger tracks each configuration command that is applied, the user who entered the command, the time that the command was entered, and the parser return code for the command. This feature includes a mechanism for asynchronous notification to registered applications whenever the configuration changes. You can choose to have the notifications sent to the syslog.

For more information, see the Configuration Change Notification and Logging feature moduleat this URL:

Using Command History

The software provides a history or record of commands that you have entered. The command history feature is particularly useful for recalling long or complex commands or entries, including access lists. You can customize this feature to suit your needs as described in these sections:

Changing the Command History Buffer Size

By default, the switch records ten command lines in its history buffer. You can alter this number for a current terminal session or for all sessions on a particular line. These procedures are optional.

Beginning in privileged EXEC mode, enter this command to change the number of command lines that the switch records during the current terminal session:

Switch# terminal history [sizenumber-of-lines]

The range is from 0 to 256.

Beginning in line configuration mode, enter this command to configure the number of command lines the switch records for all sessions on a particular line:

Switch(config-line)# history[sizenumber-of-lines]

The range is from 0 to 256.

Recalling Commands

To recall commands from the history buffer, perform one of the actions listed in Table 2-4. These actions are optional.

Recall commands in the history buffer, beginning with the most recent command. Repeat the key sequence to recall successively older commands.

Press Ctrl-N or the down arrow key.

Return to more recent commands in the history buffer after recalling commands with Ctrl-P or the up arrow key. Repeat the key sequence to recall successively more recent commands.

show history

While in privileged EXEC mode, list the last several commands that you just entered. The number of commands that appear is controlled by the setting of the terminal history global configuration command and the history line configuration command.

1The arrow keys function only on ANSI-compatible terminals such as VT100s.

Disabling the Command History Feature

The command history feature is automatically enabled. You can disable it for the current terminal session or for the command line. These procedures are optional.

To disable the feature during the current terminal session, enter the terminal no history privileged EXEC command.

To disable command history for the line, enter the no history line configuration command.

Using Editing Features

This section describes the editing features that can help you manipulate the command line. It contains these sections:

Transpose the character to the left of the cursor with the character located at the cursor.

Recall commands from the buffer and paste them in the command line. The switch provides a buffer with the last ten items that you deleted.

Press Ctrl-Y.

Recall the most recent entry in the buffer.

Press Esc Y.

Recall the next buffer entry.

The buffer contains only the last 10 items that you have deleted or cut. If you press Esc Y more than ten times, you cycle to the first buffer entry.

Delete entries if you make a mistake or change your mind.

Press the Delete or Backspace key.

Erase the character to the left of the cursor.

Press Ctrl-D.

Delete the character at the cursor.

Press Ctrl-K.

Delete all characters from the cursor to the end of the command line.

Press Ctrl-U or Ctrl-X.

Delete all characters from the cursor to the beginning of the command line.

Press Ctrl-W.

Delete the word to the left of the cursor.

Press Esc D.

Delete from the cursor to the end of the word.

Capitalize or lowercase words or capitalize a set of letters.

Press Esc C.

Capitalize at the cursor.

Press Esc L.

Change the word at the cursor to lowercase.

Press Esc U.

Capitalize letters from the cursor to the end of the word.

Designate a particular keystroke as an executable command, perhaps as a shortcut.

Press Ctrl-V or Esc Q.

Scroll down a line or screen on displays that are longer than the terminal screen can display.

Note The More prompt is used for any output that has more lines than can be displayed on the terminal screen, including show command output. You can use the Return and Space bar keystrokes whenever you see the More prompt.

Press the Return key.

Scroll down one line.

Press the Space bar.

Scroll down one screen.

Redisplay the current command line if the switch suddenly sends a message to your screen.

Press Ctrl-L or Ctrl-R.

Redisplay the current command line.

1The arrow keys function only on ANSI-compatible terminals such as VT100s.

Editing Command Lines that Wrap

You can use a wraparound feature for commands that extend beyond a single line on the screen. When the cursor reaches the right margin, the command line shifts ten spaces to the left. You cannot see the first ten characters of the line, but you can scroll back and check the syntax at the beginning of the command. The keystroke actions are optional.

To scroll back to the beginning of the command entry, press Ctrl-B or the left arrow key repeatedly. You can also press Ctrl-A to immediately move to the beginning of the line.

Note The arrow keys function only on ANSI-compatible terminals such as VT100s.

In this example, the access-list global configuration command entry extends beyond one line. When the cursor first reaches the end of the line, the line is shifted ten spaces to the left and redisplayed. The dollar sign ($) shows that the line has been scrolled to the left. Each time the cursor reaches the end of the line, the line is again shifted ten spaces to the left.

After you complete the entry, press Ctrl-A to check the complete syntax before pressing the Return key to execute the command. The dollar sign ($) appears at the end of the line to show that the line has been scrolled to the right:

Searching and Filtering Output of show and more Commands

You can search and filter the output for show and more commands. This is useful when you need to sort through large amounts of output or if you want to exclude output that you do not need to see. Using these commands is optional.

To use this functionality, enter a show or more command followed by the pipe character (|), one of the keywords begin, include, or exclude, and an expression that you want to search for or filter out:

command|{begin | include | exclude}regular-expression

Expressions are case sensitive. For example, if you enter | exclude output, the lines that contain output are not displayed, but the lines that contain Output appear.

This example shows how to include in the output display only lines where the expression protocol appears:

Switch# show interfaces | include protocol

Vlan1 is up, line protocol is up

Vlan10 is up, line protocol is down

GigabitEthernet0/1 is up, line protocol is down

GigabitEthernet0/2 is up, line protocol is up

Accessing the CLI

You can access the CLI through a console connection, through Telnet, or by using the browser.

Accessing the CLI through a Console Connection or through Telnet

Before you can access the CLI, you must connect a terminal or PC to the switch console port and power on the switch as described in the hardware installation guide that shipped with your switch. Then, to understand the boot process and the options available for assigning IP information, see Chapter 3, "Assigning the Switch IP Address and Default Gateway."

You can use one of these methods to establish a connection with the switch:

•Connect the switch console port to a management station or dial-up modem. For information about connecting to the console port, see the switch hardware installation guide.

•Use any Telnet TCP/IP or encrypted Secure Shell (SSH) package from a remote management station. The switch must have network connectivity with the Telnet or SSH client, and the switch must have an enable secret password configured.